Nowadays the use of laundry washing machines, both “simple” laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and washing-drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.
In this respect, in the present description, where not stated differently, the term “laundry treatment machine” can be referred indiscriminately to a laundry washing machine, or to a laundry washing and drying machines, or to a laundry drying machine.
Laundry washing machines are apparatuses for removing contaminants from laundry by the action of detergent and water and may have a configuration based on a rotating drum that defines a washing chamber in which laundry items are placed for washing according to one or more washing cycles/programs.
Generally, laundry washing machines are provided with controllers being configured to sense the amount of the laundry loaded in the rotating drum in order to set several parameters of the washing cycle, such as for example, the amount of water/detergent to be loaded, the cycle duration, and other washing parameters, based on the sensed laundry amount.
In some kind of known laundry treatment machines, controllers are configured to perform a control method that, at the beginning of the washing cycle, indirectly estimates the amount of laundry loaded in the rotating drum based on the water absorbed by the laundry. Indeed, the amount of water loaded during the water loading phase in a washing cycle, is proportional to the amount and type of laundry loaded in the drum. Based on the amount of water adsorbed in a prefixed time, an algorithm executed by the controller estimates the laundry quantity loaded in the drum.
This method has the problem to take long time, i.e. several minutes, to complete the estimation of the laundry load. Indeed the method may estimate the load, only after completion of the water loading procedure of the washing cycle, that generally takes up more than 15 minutes.
Furthermore, the accuracy of the estimation is low because it strongly depends on the water absorbing degree of the fabric/textile of the loaded laundry. Laboratory test made by Applicant demonstrated, for example, that two kg of sponge laundry absorbs as much water as five kg of cotton laundry.
It is therefore evident that kind of fabric/textile may strongly affect the accuracy of the estimation and, in some cases/conditions, provides completely wrong indication, unless the algorithms makes appropriate corrections to the estimated load value according to the kind of the fabric/textile, i.e. by considering the selected cycle.
However such solutions, on one side, causes the machine to performs complex algorithms and, on the other side, is limited to washing programs associated to a specific kind of fabric/textile. Indeed, remaining washing programs, such as many general washing programs frequently used by users, do not contain specific information about the fabric/textile of the loaded laundry. Moreover, this solution is affected by error due to wrong selections of the washing programs made by users.
It is further prior art to determine the amount of laundry load by performing a different procedure, which is essentially based on the time dependence of the electric power supplied by the electric motor that drives the drums, operating in a generator mode, during a revolution of the rotating drum. In this regards, for example, U.S. Pat. No. 9,096,964 B2 discloses a method for determining the load of a laundry drum of a washing machine, comprising the steps of: accelerating the laundry drum to a predetermined rotational speed, slowing down the laundry drum by operating the electric motor in generator mode, measuring electric currents flowing through the winding of the stator during the generator mode, calculating energy supplied by the electrical motor within a predetermined time interval when slowing down the rotating drum based on current and determining the load from the calculated energy.
It is the aim of the present invention to provide a method for determining the laundry load, which is simple, cheap and quick, and further improves the precision compared with the above mentioned methods.
It is thus the object of the present invention to provide a solution which allows achieving the objectives indicated above.